Sound

1. SOUND
A . Antony Alex MCA
Dr G R D College of Science – CBE
Tamil Nadu - India

2. Contents
O SoundO Sound
O Power of Sound
O Multimedia Sound Systems
O Midi Sound
O Digital Sound
Midi vs DigitalO Midi vs Digital
O Audio File Formats - Codec
O Live Session

3. Sound
O Sound is made when something vibrates.O Sound is made when something vibrates.
O The vibration disturbs the air around it.
O This makes changes in air pressure.
O These changes in air pressure move through
the air as sound waves.
O The sound waves cause pressure changes
against our ear drum sending nerveagainst our ear drum sending nerve
impulses to our brain.

4. Sound Waves
O Sound is transmitted as wave motion through aO Sound is transmitted as wave motion through a
medium such as air, water or metal.
O Waves are divided into types according to the
direction of displacement of the medium in
relation to the direction of the motion of the wave
itself.
Two basic classifications of Sound Waves areO Two basic classifications of Sound Waves are
O Transverse Waves
O Longitudinal waves.

5. Transverse Waves
O An example of a transverse wave is the
ripples on the surface of water. The vibration
of the water surface is at right angles (up
ripples on the surface of water. The vibration
of the water surface is at right angles (up
and down) to the direction of motion (out
from the disturbance).

6. Longitudinal Waves
O If the vibration is parallel to the direction ofO If the vibration is parallel to the direction of
motion, as it is with sound, the wave is
known as a longitudinal wave.

7. The three components of
sound are:
O Pitch (how high or low)O Pitch (how high or low)
O Loudness (volume)
O Timbre (tone color)

8. Pitch
O The vibration patterns of some sounds areO The vibration patterns of some sounds are
repetitive.
O Vibration patterns are also called waveforms.
O Each repetition of a waveform is called a cycle.
O We can hear frequencies between 20 hertz or
cycles (vibrations) per second (low pitches)to 20
kilohertz, i.e. 20,000 Hz (high pitches).kilohertz, i.e. 20,000 Hz (high pitches).
O Many animals can make sounds and hear
frequencies that are beyond what we can hear.

10. O To create vibrations energy is used.
Loudness
O To create vibrations energy is used.
O The greater amount of energy used the louder
the sound.
O The strength of the changes in air pressure
made by the vibrating object determines
loudness.
O As the distance from the source increases the
amount of power is spread over a greater area.amount of power is spread over a greater area.
O The amount of power per square meter is called
the intensityintensityintensityintensity of the sound.

12. Timbre (Tone color)
O It is the specific property of sound thatO It is the specific property of sound that
enables us to determine the difference
between the sound.
O An extremely broad variety of tone colors
exist because most sounds that we perceive
as pitch actually contain many frequencies.
The predominant pitch is called theThe predominant pitch is called theOO The predominant pitch is called theThe predominant pitch is called the
fundamentalfundamentalfundamentalfundamentalfundamentalfundamentalfundamentalfundamental frequency.frequency.

14. Sound Power
O Sound power is a measure of sonic energy EO Sound power is a measure of sonic energy E
per time t unit.
O The sound power level of a source is
expressed in decibels (dB)

15. Situation
and
sound source
sound power sound power
Rocket engine 1,000,000 W 180 dB
Turbojet engine 10,000 W 160 dB
Siren 1,000 W 150 dB
Heavy truck engine or
loudspeaker rock concert
100 W 140 dB
Machine gun 10 W 130 dB
Jackhammer 1 W 120 dB
Excavator, trumpet 0.3 W 115 dB
Chain saw 0.1 W 110 dB
Helicopter 0.01 W 100 dB
Loud speech,
vivid children
0.001 W 90 dB
Usual talking,
Typewriter
10−5 W 70 dB
Refrigerator 10−7 W 50 dB

16. Multimedia Sound System
O MicrophoneO Microphone
O Speakers
O Amplifier
O Equalizer
O AUDIO Drivers
O Sound CardsO Sound Cards

17. Musical Instrument Digital
Interface
O MIDI (Musical Instrument Digital Interface), is anO MIDI (Musical Instrument Digital Interface), is an
industry-standard protocol that enables electronic
musical instruments , computers and other electronic
equipment (MIDI controllers, sound cards, samplers) to
communicate and synchronize with each other. Unlike
analog devices, MIDI does not transmit an audio signal —
it sends event messages about pitch and intensity, control
signals for parameters such as volume, vibrato and
panning, cues, and clock signals to set the tempo. As an
signals for parameters such as volume, vibrato and
panning, cues, and clock signals to set the tempo. As an
electronic protocol, it is notable for its widespread
adoption throughout the music industry.

19. File Formats MIDI
O Standard MIDI (.mid or .smf)O Standard MIDI (.mid or .smf)
O MIDI Karaoke (.kar)
O XMF
O RIFF-RMID
O Extended RMID
O Extended MIDI (.xmi)O Extended MIDI (.xmi)

20. DIGITAL SOUND
O Digital audio files are like tape recordings.O Digital audio files are like tape recordings.
They store every yelp, screech and caterwaul
exactly as you make it, then reproduce them
on playback, no matter what kind of
machine they are played on.

21. MIDI vs DIGITAL
Advantages of MIDI filesAdvantages of MIDI files
O MIDI files are tiny, often 10K or less. They download
from a web page in no time and fit easily on a floppy
disk. MIDI files are ideal any time you want music to
start playing immediately.
Disadvantages of MIDI files
O Because they sound a little different when played onO Because they sound a little different when played on
different sound cards, there is no guarantee that
those lush horns won't sound like blaring trumpets
on the next guy's machine. Making universal MIDI
files is a combination of art, skill, and experience.

22. Advantages of audio files
O They can reproduce exact sounds with better-than-
CD quality, including all yelps, screeches and
caterwauls.
O On the web, audio files are best used as "streaming"O On the web, audio files are best used as "streaming"
media, where the user clicks to hear a selection as it
comes down, saving the trouble of waiting for a long
download.
Disadvantages of audio files
O They are HUGE! They can take up 10MB or more perO They are HUGE! They can take up 10MB or more per
minute of sound. Even a simple one can take several
minutes to download and play. This is why most
audio files on the web are quick snippets of 1 second
or less.

23. File Format
O An audio file format is a file format for storing audioO An audio file format is a file format for storing audio
data on a computer system. It can be a raw
bitstream, but it is usually a container format or an
audio data format with defined storage layer.
O The general approach towards storing digital audio
is to sample the audio voltage which, on playback,
would correspond to a certain level of signal in an
individual channel with a certain resolution—the
number of bits per sample—in regular intervalsnumber of bits per sample—in regular intervals
(forming the sample rate). This data can then be
stored uncompressed, or compressed to reduce the
file size.

24. O AIFF – standard audio file format used by Apple.
O aac – the Advanced Audio Coding format is based on the
MPEG2 and MPEG4 standards. aac files are usually ADTS or
ADIF containers.
O ALAC - Apple Lossless compression, a lossless compressionO ALAC - Apple Lossless compression, a lossless compression
format from Apple.
O amr - AMR-NB audio, used primarily for speech.
O atrac (.wav) – the older style Sony ATRAC format.
O m4p – A proprietary version of AAC in MP4 with Digital Rights
Management developed by Apple for use in music
downloaded from their iTunes Music Store.
O ogg – a free, open source container format supporting aO ogg – a free, open source container format supporting a
variety of codecs, the most popular of which is the audio
codec Vorbis. Vorbis offers compression similar to MP3 but is
less popular.

25. O ra & rm – a Real Audio format designed for streaming audio over
the Internet. The .ra format allows files to be stored in a self-
contained fashion on a computer, with all of the audio data
contained inside the file itself.
O raw – a raw file can contain audio in any codec but is usually usedO raw – a raw file can contain audio in any codec but is usually used
with PCM audio data. It is rarely used except for technical tests.
O TTA - The True Audio, real-time lossless audio codec.
O wav – standard audio file container format used mainly in
Windows PCs.
O wma – the popular Windows Media Audio format owned by
Microsoft. Designed with Digital Rights Management (DRM)
abilities for copy protection.
Au – the standard audio file format used by Sun, Unix and Java.O Au – the standard audio file format used by Sun, Unix and Java.
O MP3-MP3 is one of the most popular sound formats for music
recording. The MP3 encoding system combines good compression
(small files) with high quality. Expect all your future software
systems to support it.

26. Live Session
O Creating MIDI AudioO Creating MIDI Audio
O Creating Digital Audio
O Mono Stereo
O Digital Audio(DTS)
O Codec
O File ConversionO File Conversion

27. History of Audio Sound in
Multimedia
O No SoundO No Sound
O Mono
O Music
O Digital
O Stereo
O Digital
O DTS
O Arena
O Dolby Digital
Cube
O Dolby Digital
O Cube
O 3D Surround System
O Virtual 3D Surround System